Assertion:Zona pellucida do not dissappears when blastocyst reaches the uterus .

Reason:Role of zona pellucida is to check the implantation of the blastocyst at the veginal site.

Both assertion and reason are wrong
Blastocyst is the next stage of embryo after morula, consisting of more than 100 cells(blastomeres).  As a blastocyst is formed, zona pellucida become thinner and finally disappears. Zona pellucida prevents sticking of growing embryo to uterine wall.
So, in the absence of zona pellucid,  blastocyst gets embedded into the thickened inner wall of the uterus through the process of implantation, about six days after fertilisation . Then this stage is followed by gastrula stage.
Morula is the stage of embryonic development which is still surrounded by zona pellucida.

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both assertion and reason are incorrect.

becauseIn humans, five days after the fertilization, the blastocyteperforms zona hatching i.e.the zona pellucida degenerates and decomposes. and role of zona pellucida is to check that after insemination of one sperm, the other do not reach inside the ovum.

hope this helps u.

ChEErs!!! :)

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